Field of the Invention
The present invention concerns: a method to determine a complete parameter of a pulse sequence with multiple pulse sequence modules for a magnetic resonance examination apparatus and a corresponding device; and a corresponding computer-readable data storage medium.
Description of the Prior Art
For medical examination of a patient in a magnetic resonance scanner (MR scanner), different pulse programs (MR pulse sequences) are used with which different properties of the tissue can be determined. In these pulse programs, an individual radio-frequency pulse (RF pulse) or a sequence of RF pulses is radiated into the tissue, which is located in a strong magnetic field. By the acquisition of the resulting magnetic resonance signal (also called MR signal or free induction decay, FID) and subsequent Fourier transformation thereof, images of the examined tissue can be acquired.
For example, an MR pulse can include one or more different sequence modules (for example kernel, saturator, EKG trigger) that are normally emitted (activated) periodically. In this case, the sequence modules are embedded in a structure composed of interleaved loops, of which each realizes a periodicity of the MR measurement, for example lines in k-space, averagings or phases.
The sequence modules that are used are characterized by (among other things) their frequency, duration and energy that are applied in their use. For example, in order to indicate the duration of an examination measurement to a user, the total duration of all applications with the different sequence modules of the sequence is calculated.
The total energy of the measurement can be calculated in a corresponding manner. The applied power and the specific absorption rate (SAR) can then be calculated from the two values. Using the specific absorption rate, for example, a decision can then be made as to whether a measurement can be implemented without endangering the patient. In addition to the total duration and total energy of a measurement, time intervals with consistent power represent an important variable for describing a measurement.
In the prior art, formulas are used in order to determine the aforementioned parameters (such as the total energy or the total duration) of the pulse sequence. It has proven to be disadvantageous that these formulas must be adapted for every change to the loop structure. Depending on an examination protocol setting—i.e. depending on whether an option is active or not—the loop structure of the pulse sequence changes, and the calculation formulas for energy and measurement duration that match this loop structure thereby change. It is consequently necessary to always adapt the calculation formulas when the pulse sequence changes in order to avoid incorrect calculations.
This leads to an increased implementation cost and a high tendency toward error, since typical MR sequences have excessively complex loop structures with a plurality of different pulses.